\section{Discussion}
It was found that the gripper is best able to resist a force applied in the y-directions of the tool frame seen in figure \ref{fig:gripper:1}. It is however more difficult to resist a force applied in the x-directions, and the most difficult directions are the z-directions. This seems to be a reasonable and expected result for the given scene and gripper, as the gripper fingers squeezes together along the y-axis.\\

\noindent The CMCPP quality measure gives a good linear relationship between the grasp quality measure and the successrate. The quality measure does not reach a lower than 25\% successrate, which which might be due to the fact that the applied force is too small. Unfortunately the CMCPP measure does not give meaning with respect to the applied force, but it is however expected to be more simple and computationally efficient.\\

\noindent The Wrench Space quality measure was constructed such that the quality measure should indicate directly what force the grasp is able to resist. The ideal result should be that the successrate is 100\% if the quality measure is higher than the applied force and 0\% if the quality measure is less than the applied force. Figure \ref{fig:results:wrench:a} almost shows this relationship, but 0\% is never reached. \\
\noindent By applying more force, figure \ref{fig:results:wrench:b} to \ref{fig:results:wrench:d} shows that the lowest quality measures gets increasingly closer to 0\%. Unfortunately only few grasps results in high quality measures. Therefore the data is not as significant as for the low quality measures. It is however clear that if large forces are applied, even higher quality grasps will fail. This indicates that the wrench space does not give the correct prediction of the grasp quality compared to the simulation. This might both be due to limitations of the simulator, and due to limitations of the chosen wrench space method.\\
The wrench space has one large drawback. There will be a large difference between applying one force of 2N, or two forces on 1N in the same point. The same issue exists for the torques acting on the object. This issue have been addressed by scaling the forces and torques respectively. Although a scaling is introduced to remove a problem it is quite possible that it introduces others which compromises the results of the Wrench Space.\\

\noindent The influence of the coefficient of friction is examined in figure \ref{fig:results:wrench_friction}. In theory the coefficient of friction should not influence the results. It is however seen that increasing the coefficient of friction, seems to increase the successrate for all quality measures. Even though the break between success and failure is expected to be at $9.1N$, it seems that the break changes somewhat when changing the coefficient of friction.\\

\noindent
Based on the general erratic quality of the results a number of different explanation are considered. One explanation could be that the Grasp Wrench Space is an inadequate measure for grasp quality. A second explanation could be that the contact generation is inadequate in comparison with the real world. A third explanation could be that ODE simulator simulates the contacts in a too simple way and thereby spoils the outcome. In the lack of a ground truth it is difficult to be more specific in what the actual problems are other than suggesting that it probably is a combination of the three mentioned issues.